1. Field of the Disclosure
The present invention relates to a circuit breaker, and more particularly, to a circuit breaker including a lug-type terminal block.
2. Background of the Disclosure
In general, a circuit breaker is an electrical device that manually opens and closes an electrical circuit by a handle, or that protects load devices and circuits by detecting an abnormal current such as a short-circuit current and automatically breaking the circuits.
The circuit breakers include a thermal adjustable type circuit breaker for adjusting the rated current and a thermal fixable type circuit breakers for fixing the rated current at a predetermined value.
Although the thermal fixable type circuit breaker may use different components from those of the thermal adjustable type circuit breaker, it usually uses the same components as the thermal adjustable type circuit breaker for component commonality and only the operating parts are fixed to prevent the user from arbitrarily adjusting the rated current.
Hereinafter, a trip device for a circuit breaker according to the conventional art which implements the thermal adjustable type circuit breaker and the thermal fixable type circuit breaker will be described below with reference to the accompanying FIGS. 1 and 2.
As shown in FIG. 1, a conventional circuit breaker includes a case 10, a fixed contact 20 fixedly mounted in the case 10, a movable contact 30 configured to be brought into contact with and separated from the fixed contact 20, a switching mechanism 40 for opening and closing the movable contact 30, and a trip device OT that detects an abnormal current such as a short-circuit current and automatically triggers the switching mechanism 40 to a trip position.
As shown in FIG. 1, the trip device OT includes a crossbar 70 rotatably installed to perform the trigger function and bimetal 50 that is curved upon the occurrence of an abnormal current and presses and rotates the crossbar 70 by a pressure member 52 formed on one end.
In this case, the crossbar 70 is installed to be movable in the direction of a rotating shaft of the crossbar, as shown in FIG. 2.
A contact surface 52a of the pressure member 52 of the bimetal 50 slopes in the direction of movement of the crossbar 70.
This is to adjust the gap between the bimetal 50 and the crossbar 70, more precisely, the gap between the contact surface 52a of the pressure member 52 of the bimetal 50 and a contact surface 70a of the crossbar 70, by adjusting the position of the crossbar 70 on a rotating shaft, when it is desired to implement the thermal adjustable type circuit breaker.
Hereinafter, the operational effects of the trip device OT for a circuit breaker according to the conventional art will be explained.
That is, when an abnormal current is applied to the conventional circuit breaker, the bimetal 50 bends to the left in FIG. 1 when heated by the applied current, and rotates the crossbar 70 by means the pressure member 52 and unlocks a latch (not shown) of the switching mechanism 40. Once the latch (not shown) is unlocked, the movable contact 30 is quickly separated from the fixed contact 20 by the elastic force of a trip spring (not shown) of the switching mechanism 40.
For this procedure, the trip device OT for the conventional circuit breaker is equipped with the crossbar 70 which is movable in the direction of the rotating shaft and the contact surface 52a of the pressure member 52 of the bimetal 50 which slopes in the direction of movement of the crossbar 70.
As such, the trip device OT for the conventional circuit breaker is able to adjust the gap between the bimetal 50 and the crossbar 70 by adjusting the position of the crossbar 70 on the rotating shaft, thereby implementing the thermal adjustable type circuit breaker for rated current adjustment.
Meanwhile, when implementing the thermal fixable type circuit breaker for fixing the rated current, the trip device OT for the conventional circuit breaker uses the same types of crossbar 70 and bimetal 50 to achieve component commonality, and fixes the crossbar 70 at a predetermined position on the rotating shaft so that the gap between the bimetal 50 and the crossbar 70 is fixed at a predetermined value.
In the trip device OT for the conventional circuit breaker, however, the crossbar 70 is placed into an unintended position due to any distribution or assembly error in the components. This changes the gap between the bimetal 50 and the crossbar 70. As a result, a scatter diagram of overcurrent time is large, and the reliability of a trip operation is deteriorated.